Switch contact structure

ABSTRACT

A switch contact structure including a pair of pivotally mounted, horizontally disposed contact fingers slidably positioned to laterally engage a blade or stab-type electrical contact therebetween, and a pair of vertically disposed flexible, resilient U-shaped shunts each having an upper arm and a lower arm; the lower arm being rigidly secured. The upper arms of the U-shaped shunts are fixed to electrically conductive lever arms protruding outwardly and laterally from the respective contact fingers. A magnetic field developed by a reverse current flow pattern through the arms of the U-shaped shunts causes a vertical displacement of the upper arm of the U-shaped shunts which imparts a rocking motion to the contact fingers which increases the contact pressure between the contact fingers and the stabtype electrical contact. The magnitude of the contact pressure is controlled by adjusting the active length of the lever arms by varying the lateral distance between the U-shaped shunts and the contact fingers.

United States Patent [72] Inventor Alfred W. l-lodgson Orchard Park, N.Y. [21] App]. No. 30,514 221 Filed Apr. 21, 1970 [45] Patented Aug. 31, 1971 [73] Assignee Westinghouse Electric Corporation Pittsburgh, Pa.

[54] SWITCH CONTACT STRUCTURE 7 Claims, 7 Drawing Figs.

[52] US. Cl 200/170 R, 200/ 166 E [51] Int. (I H0lh 1/54 [50 Field otSearch 200/170 R, 170 A, 166 E [56] References Cited UNITED STATES PATENTS 2,777,921 1/1957 Latour 2001170 A 3,154,662 10/1964 Heupel et al 200/170 A 3,l84,573 5/1965 Latour 2001166 E 3,196,240 200/166 E X 7/1965 Latour 3,235,697 2/1966 Rodeseike Primary Examiner-H. 0, Jones Attorneys-F. H. Henson, M. P. Lynchand C. F. Renz ZOO/166 E ABSTRACT: A switch contact structure including a pair of pivotally mounted, horizontally disposed contact fingers slidably positioned to laterally engage a blade or stab-type electrical contact therebetween, and a pair of vertically disposed flexible, resilient U-shaped shunts each having an upper arm and a lower arm; the lower arm being rigidly secured.- The upper arms of the U-shaped shunts are fixed to electrically conductive lever arms protruding outwardly and laterally from the respective contact fingers. A magnetic field developed by a reverse current flow pattern through the arms of the U-shaped shunts causes a vertical displacement of the upper arm of the U-shaped shunts which imparts a rocking motion to the contact fingers which increases the contact pressure between the contact fingers and the stab-type electrical contact. The magnitude of the contact pressure is controlled by adjusting the active length of the lever arms by varying the lateral distance between the U-shaped shunts and the contact fingers.

SHEET 1 BF 4 PATENTEU M1831 l9?! INVENTOR Alfred W. Ho gson WMJ L X M4 ATTORN EY WITNESSES SWITCH CONTACT STRUCTURE BACKGROUND OF THE INVENTION The technique of utilizing the magnetic fields of a pair of resilient U-shaped current shunts to increase switch contact pressure is not new as is evidenced by the teachings of U.S. Pat. No. 2,894,101.

The application of this technique heretofore however has been limited to a configuration in which the movable arms of the respective U-shaped shunts move toward one another in a closing relationship in response to the magnetic fields developed by the reverse current flow. The contact fingers comprising a switch contact structure are affixed directly to the movable arms of the U-shaped shunts such that the movement of the arms which corresponds in direction to the lateral engaging movement of the contact fingers directly increases the lateral engaging action, or contact pressure, of the contact fingers. The contact pressure is therefore, solely a function of the current flow and the magnetic field.

SUMMARY OF THE INVENTION The invention relates to improved utilization of a pair of U- shaped reverse current shunts for increasing contact pressure of a switch contact structure.

The action of a pair of vertically disposed U-shaped reverse current shunts is transmitted to a pair of horizontally disposed contact fingers through lever arms extending from the contact fingers to impart a rocking, or tilting motion to the contact fingers to increase the contact pressure between the contact fingers and a stab-type electrical contact. The contact pressure established by this rocking motion is a function of the active length of the lever arm, the square of the current flow, and the spacing of the arms of the U-shaped reverse current shunts.

The invention will become more readily available from the following exemplary description in connection with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. I is a top view of an electrically disengaged isolating switch apparatus in which the invention is embodied;

FIG. 2 is a top view of the apparatus of FIG. 1 in an electrically engaged position;

FIG. 3 is a front perspective view of a high-voltage cabinet including the isolating switch apparatus of FIGS. 1 and 2;

FIG. 4 is a side elevational view of one switch contact structure of the embodiments of FIGS. 1 and 2;

FIG. 5 is a cross-sectional view taken along the line AA of FIG. 4;

FIG. 6 is a cross-sectional view taken along the line B-B of FIG. 4; and

FIG. 7 is a cross-sectional view taken along the line C-C of HG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2 there is illustrated a three-pole isolating switch assembly 10 including switch contact structures 20. The isolating switch assembly 10 is provided with a frame 100 comprising a front panel 102, a back panel 104 made of insulating material, and side plates 106 and 108 rigidly secured together in the form of an open rectangle as viewed from the top. The back panel 104 is provided with apertures 105 through which the spring-biased contact fingers 30 of the switch contact structures respectively are projected and retracted by the action of a cam-shutter mechanism 200 in response to the rotative motion of a handle mechanism 60.

Side plates I06 and 108 are provided at their upper edges with outwardly extending flanges 116 and 118 which slidably bear on guide rails 126 and 128 of the cabinet 140 of FIG. 3, thereby supporting and allowing slidable movement of the isolating switch assembly 10 into and out of the cabinet. The

arrangement of structure within the frame permits a relatively unobstructed flow of cooling air through the isolation switch assembly 10. V

The switch contact structures 20 are secured to a slidably mounted carrier 150 for slidably engaging guide. rollers 152 of FIGS. 1, 2 and 4. Backward and forward movement of the carrier 150 is provided by operating linkage 160 in response to the rotative positioning of the handle mechanism 60 between an ON and OFF position. Forward movement of the carrier 150 produced by rotating handle mechanism 60 to the ON position results in the projection of the contact fingers 30 through the apertures in the back panel 104 as illustrated in FIG. 2 electrically engage the input power stab contacts which are vertically mounted on the back panel 109 of the cabinet. The backward carrier movement produced by rotating the handle mechanism 60 to the OFF position disengages the contact fingers 30 from the respective stab contacts 130 and retracts the contact fingers to the position shown in FIG. 1. i

A safety feature is provided by the cam-shutter mechanism 200 which includes a finger 201 extending through a shutter 202 and operating to position the shutter 202 to cover the apertures 105 and consequently the stab contacts 130 in response to movement of the carrier produced by the OFF positioning of the handle mechanism 60, and operating to uncover these apertures in response to movement produced by the ON positioning of the handle mechanism. The apertures 105 are uncovered when the corresponding cutout areas 181 of the shutter 202 are brought into registry therewith.

Molded insulator member 131 which is associated with the I stab contacts 130 cooperates with vertical flanges 104A extending rearwardly from the back panel 104 to provide horizontal alignment of the spring-biased contact fingers 30 with the stab contacts 130.

The present invention is directed particularly to the switch contact structure 201 which is illustrated in FIGS. 1, 2 and 4. FIGS. 5, 6 and 7 are sectional views of FIG. 4. Elongated contact fingers 30 are secured in an aligned, movable relationship with a support member 50 by shoulder bolts 52 and 54 which pass through clearance holes 51 and 53 respectively. Contact surfaces 32 of the contact fingers 30 which extend beyond the support 50 are biased toward each other by a spring 55. The spring 55 is maintained in a biasing relationship with the contact fingers 30 by the shoulder bolt 52. The spring loading of the contact fingers by spring 55 biases the contact surfaces 32 in a closed contacting relationship in the absence of the stab contact 130 therebetween.

The shoulder bolt 54 extends laterally through clearance hole 53in the contact fingers 30 and support 50 to a distance beyond the sides 50A of the support 50 so as to provide physical contact between the contact fingers 32 and the support 50 at the dome-shaped pivot points 34. This permits movement of the contact fingers 30 about the pivot points 34 in response to engagement and disengagement of the contact fingers 30 and the input power stab contact 130. A pin 56 which is rigidly secured in the support 50 loosely engages the contact fingers 30 through elongated apertures 35 to maintain alignment of the contact fingers.

Protruding laterally from the sides of the contact fingers 30 opposite to the pivot points 34 are electrically conductive lever arms 36 which are secured to the upper arms 70A of vertically oriented U-shaped current shunts'70. The lower arms 70B of the U-shaped shunts are secured to an electrical connector 80 which in turn is rigidly affixed to a mounting bracket 82. The U-shaped shunts are preferably formed of copper with the arms 70A and 70B exhibiting flexible, resilient characteristics.

A flow of current indicated by the arrows of FIGS. '2 and 4 from the. stab contact 130 through the contact fingers 30 and the U-shaped shunts 70 to the electrical connector 80 will with the stab contact 130.

It will be observed that a current flow through the contact fingers 30 of FIG. 2 is in the same direction. As a result, the magnetic field generated by this current flow tends to draw the contact surfaces 32 toward each other and thereby increase the contact pressure between the contact surfaces 32 and the sides of the stab contact 130. The current flow in the upper arms 70A of the U-shaped shunt is in a direction opposite to the current flow in the lower arms 70B of the respective shunts. As a result, the magnetic forces produced by this reverse current flow pattern act in such a manner as to urge the upper arms 70A away from the lower arms 70B. Since the lower arms 70B are held stationary by the mounting bracket 82, the upper arms are vertically displaced in response to the magnetic field created by the reverse current flow. The upward vertical displacement of the upper arm 70A acting through the lever arms 36 imparts a rocking or twisting motion to the contact fingers 30 about the longitudinal axis of the contact fingers which passes through the pivot points 34 as illustrated in FIGS. 5, 6 and 7. This rocking motion further compresses the spring 55 and thereby increases the contact pressure between the contact surfaces 32 and the stab contact 130. The clearance hole 51 permits rocking of the contact fingers 30 relative to the shoulder bolt 52.

The spring 55 as shown in FIG. 6 is maintained in compression between a retainer ring 90 and an electrical insulating bushing 92 by the shoulder bolt 52 so as to bias the contact fingers 30 toward each other. The shoulders 92A and 94A of electrical insulating bushings 92 and 94 are inserted in the contact fingers 30 to electrically insulate the contact fingers 30 from the spring 55 to prevent spring damage caused by current flow therethrough. The contact finger rocking motion produced by the reverse current in the U-shaped shunts 70 tilts the contact fingers 30 to increase the contact pressure between the contact surfaces 32 and the stab contact 130. The design of the spring 51 is such as to cause the lower portion of the coils to be compressed to a solid condition in response to a preset contact finger tilting motion to thereby limit the tilting or rocking motion of the contact fingers and translate the upward displacement of the arms 70A of the U-shaped shunt directly into increased contact pressure at point A.

While the displacement of the upper arm 70A of the U- shaped shunts in a function of the reverse current flow, the magnitude of contact pressure generated by the action of the U-shaped shunts 70 can be controlled by changing the position of the upper arm 70 in slot 36A of the lever arms 30 so as to vary the active lever arm distance d between the shunt arms 70A and the pivot points 34 as shown in FIG. 5. It is apparent that for the same reverse current flow the contact pressure developed at point A by the contact surfaces 32 will increase as d becomes large and will decrease as d becomes small.

In addition to the mechanical advantage provided by lever arms 36, further mechanical advantage is provided by the distance r of FIG. 7 corresponding to the distance between the longitudinal axis 1 of the contact fingers 30 and point A about which the contact surfaces 32 pivot.

The contact pressure can be further altered by varying the length of the arms 70A and 708 as well as the spacing between the arms.

In addition to providing the compatibility of adjusting contact pressure, the vertically positioned U-shaped shunts minimize the lateral dimension of the switch contact structure over the conventional contact structure employing horizontally positioned U-shaped shunts, and thus permits desirable compact lateral packaging of the contact structures in assemblies such as the isolation switch assembly of FIGS. 1 and 2.

I claim:

l. A switch structure comprising, a stab-type electrical contact means, movably mounted elongated contact finger means, means biasing said contact finger means in lateral electrical engagement with said stab-type electrical contact means, lever arm means extending from said contact finger means, and flexible, resilient Ushaped reverse current shunt means having a first arm rigidly secured and a second arm in contact with said lever arm means, said U-shaped reverse current shunt means imparting a rocking motion to said contact finger means through said lever arm means in response to displacement motion of said first arm resulting from magnetic forces developed by reverse current flow through the upper and second arms of said U-shaped reverse current shunt means, said rocking motion occurring about the longitudinal axis of said contact finger means and operating to increase the contact pressure between said contact finger means and said stab-type electrical contact means.

2. A switch structure as claimed in claim l wherein said displacement motion of said second arm is substantially perpendicular to the lateral engaging action of said contact finger means, the increase in contact pressure provided by the U- shaped reverse current shunt means being in part a function of the distance between the contact finger means and the point at which said second arm contacts said lever arm means.

3. In an electric switch apparatus, the combination, of, a stab-type electrical contact means, a support plate means, a first and a second elongated contact finger means, each having a contact surface on one side near one end, said first and second contact fingers means movably mounted on said support plate means with side contact surfaces positioned beyond said support plate means and facing each other, means biasing said contact surfaces toward each other for laterally engaging said stab-type electrical contact, a first lever arm means extending from the side of said first contact finger means opposite to said contact surface, a second lever arm means extending from the side of said second contact finger means opposite to said contact surface, and a first and second U-shaped reverse-current shunt means operatively associated with said first and second lever arm means respectively, each U-shaped reverse current shunt means having flexible, resilient first and second arms, said first arms rigidly secured and said second arms in contact with said lever arm means, said first and second U-shaped reverse current shunt means imparting a rocking motion to said first and second contact finger means through'said first and second lever arm means respectively in response to displacement motion of said second arms produced by magnetic forces resulting from reverse current flow through the first and second arms of said first andsecond U-shaped reverse current shunt means, said displacement motion being substantially perpendicular to the lateral engaging action of said contact finger means, said rocking motion occurring about the longitudinal axis of said contact finger means.

4. In an electric switch apparatus as claimed in claim 3 wherein said first and said second contact finger means include a dome-shaped pivot point on the side of the contact finger means opposite to said lever arm means, said domeshaped pivot point contacting said support plate means to implement said rocking motion.

5. In an electric switch apparatus as claimed in claim 3 wherein said rocking motion tilts said contact surfaces causing a first portion of the contact surface to be displaced from said stab-type electrical contact while increasing the contact pressure between the second portion of the contact surfaces and the stab-type electrical contact.

6. In an electric switch as claimed in claim 5 wherein said means biasing includes a spring member acting in compression against said contact finger means to urge said contact surfaces toward each other for laterally engaging said stab-type electrical contact, the design of said spring member being such as to cause the coils of said spring to go to a solid condition in response to a predetermined displacement of said lower portion of said contact surfaces from said stab-type electrical contact.

7. In an electric switch as claimed in claim 3 wherein said first and second lever arm means include means for adjustably varying the lever arm distance between said second arms and said contact finger means. 

1. A switch structure comprising, a stab-type electrical contact means, movably mounted elongated contact finger means, means biasing said contact finger means in lateral electrical engagement with said stab-type electrical contact means, lever arm means extending from said contact finger means, and flexible, resilient U-shaped reverse current shunt means having a first arm rigidly secured and a second arm in contact with said lever arm means, said U-shaped reverse current shunt means imparting a rocking motion to said contact finger means through said lever arm means in response to displacement motion of said first arm resulting from magnetic forces developed by reverse current flow through the upper and second arms of said U-shaped reverse current shunt means, said rocking motion occurring about the longitudinal axis of said contact finger means and operating to increase the contact pressure between said contact finger means and said stab-type electrical contact means.
 2. A switch structure as claimed in claim 1 wherein said displacement motion of said second arm is substantially perpendicular to the lateral engaging action of said contact finger means, the increase in contact pressure provided by the U-shaped reverse current shunt means being in part a function of the distance between the contact finger means and the point at which said second arm contacts said lever arm means.
 3. In an electric switch apparatus, the combination, of, a stab-type electrical contact means, a support plate means, a first and a second elongated contact finger means, each having a contact surface on one side near one end, said first and second contact fingers means movably mounted on said support plate means with side contact surfaces positioned beyond said support plate means and facing each other, means biasing said contact surfaces toward each other for laterally engaging said stab-type electrical contact, a first lever arm means extending from the side of said first contact finger means opposite to said contact surface, a second lever arm means extending from the side of said second contact finger means opposite to said contact surface, and a first and second U-shaped reverse current shunt means operatively associated with said first and second lever arm means respectively, each U-shaped reverse current shunt means having flexible, resilient first and second arms, said first arms rigidly secured and said second arms in contact with said lever arm means, said first and second U-shaped reverse current shunt means imparting a rocking motion to said first and second contact finger means through said first and second lever arm means respectively in response to displacement motion of said second arms produced by magnetic forces resulting from reverse current flow through the firSt and second arms of said first and second U-shaped reverse current shunt means, said displacement motion being substantially perpendicular to the lateral engaging action of said contact finger means, said rocking motion occurring about the longitudinal axis of said contact finger means.
 4. In an electric switch apparatus as claimed in claim 3 wherein said first and said second contact finger means include a dome-shaped pivot point on the side of the contact finger means opposite to said lever arm means, said dome-shaped pivot point contacting said support plate means to implement said rocking motion.
 5. In an electric switch apparatus as claimed in claim 3 wherein said rocking motion tilts said contact surfaces causing a first portion of the contact surface to be displaced from said stab-type electrical contact while increasing the contact pressure between the second portion of the contact surfaces and the stab-type electrical contact.
 6. In an electric switch as claimed in claim 5 wherein said means biasing includes a spring member acting in compression against said contact finger means to urge said contact surfaces toward each other for laterally engaging said stab-type electrical contact, the design of said spring member being such as to cause the coils of said spring to go to a solid condition in response to a predetermined displacement of said lower portion of said contact surfaces from said stab-type electrical contact.
 7. In an electric switch as claimed in claim 3 wherein said first and second lever arm means include means for adjustably varying the lever arm distance between said second arms and said contact finger means. 